Direct current system of electric distribution



Nov. 30, 1943. H. M. MARTIN 2,335,682

DIRECT CURRENT SYSTEM OF ELECTRIC DISTRIBUTION Filed Dec. 22, 1941Inventor- I Harold M. Martin His Attorne g.

Patented Nov. 30, 1943 DIRECT CURRENT SYSTEM' OF ELECTRIC DISTRIBUTIONHarold M. Martin, Schenectady, N. Y., assignor to General ElectricCompany, a corporation of New York Application December 22, 19.41,Serial No. 423,891

6 Claims.

My invention relates to direct current systems of electric distributionand particularly to such systems in which it is very essential that thedistribution system shall be energized at a substantially constantvoltage.

Heretofore, it has been proposed to provide in such systems an auxiliarystand-by storage battery which is normally maintained in a chargedcondition and which isconnected to the direct current distributionsystem so that it supplies current thereto in case the main source ofcurrent therefor fails. Such systems have usually consisted of a batterywhich normally floated across the distribution circuit and have beenprovided with suitable means for charging the battery while the mainsource of current was connected to the distribution circuit. Such priorsystems, however, were not operative in connection with batteries, suchas the well known Edison type, which require a charging voltage that ismuch higher than their normal discharging voltage and which, also, havea relatively large voltage drop between their fully charged and theirfully discharged values.

One object of my invention is to provide an arrangement of apparatuswhereby batteries of the Edison or similar type may be used as auxiliarysources of power for a direct current distribution circuit in case thesource of power therefor fails.

Another object of my invention is to provide an arrangement of apparatuswhereby a storage battery of the Edison or similar type may be rechargedand maintained in a sufficiently charged condition while the directcurrent distribution circuit is being supplied from its main source ofcurrent and is automatically connected to the distribution circuit whenthe main source of power therefor fails and whereby the voltage of thedistribution circuit is maintained at a predetermined value while thebattery is supplying current thereto.

In accordance with my invention, I provide a direct currentdynamoelectric machine in series with the battery across thedirect-current distribution circuit and control the volage of thedynamoelectric machine in response to the battery voltage while thedistribution circuit is-being supplied from the main source of currentso that the dynamoelectric machine acts as-a booster to increase thevoltage applied to'the battery -,to a 1 buck down the battery voltagewhen it is too high and to boost the voltage of the battery when thevoltage thereof is below the circuit voltage.

My invention will be better understood from the following descriptionwhen taken in connection with the accompanying drawing, the singlefigure of which diagrammatically illustrates a three-wire direct currentsystem of distribution embodying my invention, and its scope will bepointed out in the appended claims.

Referring'to the drawing, l represents a threewire direct currentdistribution circuit which is normally connected-to a three-wire directcurrent supply circuit 2 by the two contactors 3 and 4 whichrespectively connect together the positive conductors of the circuits land 2 and the negative conductors of the circuits 1 and 2. The openingof the contactors 3 and 4 is effected simultaneously in response toafailure-of the supply circuit 2 by means of a voltage responsive relay 5and an associated control relay 6 connected between the positiveandnegative conductors of the supply circuit 2. The voltage relay 5controls contacts I in an energizing circuit for the control relay 6 sothat the relay B'is energized when the supply circuit voltage is above apredetermined value and is ,deenergized when the supply circuit voltageis below a predetermined value. When energized, the control relay 6 inturn completes a series energizing circuit for the operating windings ofthe contactors 3 and 4 between the positive and negative .conductors ofthe supply circuit 2.

.For supplying current to the distribution circuitl when the main supplycircuit 2 is disconnected therefrom, I provide two storage batteries Band B respectively connected between the positive and neutral conductorsand between the neutral and negative conductors of the distributioncircuit. I also provide a motor-generator set .8 comprising a directcurrent motor 9, connected between the positive and negative conductorsof the distribution circuit I, and two dynamoelectric machines It) and.H driven by the motor 9. The armature winding. [2 of the.dynamoelectricmachine I 0 is connected in series withlthe battery-Bbetween the positive and the neutral conductors of the distributioncircuit I,

and'the armature Winding l3 of thedynamoelectric-machine I l isconnected in series with thelbattery B between the neutral and negativeconductors of the distribution circuit 1. The dynamoelectric machines Itand H are respec- .tively provided with :the field windings l5 and 16,which .are respectively. arranged to be :con-

nected between the positive and neutral conductors and between theneutral and negative conductors of the direct current circuit I in amanner which will hereinafter be described.

In accordance with my invention, I control the energizations of thefield windings I and I6 so that when the main supply circuit 2 isconnected to the distribution circuit I, the voltages of thedynamoelectric machines I!) and II are respectively controlled inresponse to the voltages across the batteries B and B, and when thesupply circuit 2 is disconnected from the distribution circuit I, thevoltages of the dynamoelectric machines IS and II are respectivelycontrolled in response to the voltages between the positive and neutralconductors and between the neutral and negative conductors of thedistribution circuit I.

In the particular embodiment of my invention shown in the drawing, Iaccomplish this result by providing suitable voltage regulators I9 and2!] for respectively controlling the energizations of the field windingsI5 and IS. The voltage regulator I9 comprises two fixed resistors 23 and24 and two adjustable resistors 25 and 25, which are so connected as toform a Wheatstone bridge. The two fixed resistors 23 and 24 and anotherfixed resistor 21 are connected in series between the positive andneutral conductors of the distribution circuit I, and the two adjustableresistors 25 and 25 are connected in a series circuit which is inparallel with the series-connected fixed resistors 23 and 24. Oneterminal of the field winding I5 is connected to a point between theseries-connected fixed resistors 23 and 2 3, and the other terminal ofthe field Winding I5 is connected to a point between theseries-connected adjustable resistors 25 and 26. The resistances ofresistors 25 and 26 are arranged to be adjusted simultaneously by asuitable operating magnet 29 comprising a voltage winding 28, which isarranged to be connected so as to be energized in response to thevoltage of the battery B when the control relay 6 is energized and inresponse to the voltage between the positive and neutral terminals ofthe distribution circuit I when the relay 6 is deenergized. Since thebattery charging Voltage, which the regulator I 9 maintains constantwhile the distribution circuit I is being supplied with current from themain supply circuit 2, is materially higher than the distributioncircuit voltage which the regulator I9 maintains constant while thedistribution circuit is being supplied with current from the battery B,suitable adjustable resistors 30 and SI are respectively connected inseries with the voltage winding 23 when it is connected across thebattery B and I when it is connected between the positive and neutralconductors of the distribution circuit I so as to effect the propercalibration of the regulator whenever the connection of the voltagewinding 28 thereof is changed. The adjustable resistors 25 and 25 are socontrolled by the magnet 29 that an increase in the energization of 'thef magnet 29 effects an increase in the resistance of the resistor 25 anda decrease in the resistance of the resistor 26. During the normaloperation of the system when the machine I0 is operating as a booster toincrease the voltage across the battery B to the desired charging value,a relay 32, which is controlled by the position of the relay 6, connectsthe adjustable resistors 25 and 26 so that the resistors 23 and 26 arerespectively in the adjacent branches of the Wheatstone bridge which areconnected tothe positive conductor of the distribution circuit I throughthe fixed resistor 21, and the resistors 24 and 25 are respectively inthe adjacent branches of the Wheatstone bridge which are connected tothe neutral conductor of the distributor circuit I. Therefore, when thecharging voltage is too high, the resistances of the resistors 25 and 25are adjusted relatively to each other by the magnet 25 so as to decreasethe current through the field Winding I5 and thereby effeet a decreasein the voltage of the machine It which is then operating as a booster.When the charging voltage is too low, the relative resistances of theresistors 25 and 26 are adjusted by the magnet 29 so as to increase thecurrent through the field winding I5 and thereby efiect an increase inthe voltage of the machine I 0. When the main supply circuit 2 fails sothat the battery B'supplies current to the distribution circuit I andthe regulator I9 operates to maintain a constant voltage between thepositive and neutral conductors of the distribution circuit I, it isnecessary to decrease the excitation of the machine It so as to decreasethe voltage thereof when the distribution circuit voltage is too low.Therefore, when the main supply circuit 2 fails so that the controlrelay 5 is deenergized, the relay 32 operates to change the connectionsof the resistors 25 and 26 so that resistors 23 and 25 are respectivelyin the adjacent branches of the Wheatstone bridge which are connected tothe positive conductor of the distribution circuit I through theresistor 27, and the resistors 24 and 25 are respectively in theadjacent branches of the Wheatstone bridge which are connected to theneutral conductor of the distribution circuit I. When the distributioncircuit voltage is too low while the battery B is supplying current tothe circuit I, the relative resistances of the resistors 25 and 28 areadjusted by the magnet 28 so as to decrease the current through thefield winding I5 and thereby effect a decrease in the voltage of themachine I 5. When the distribution circuit voltage is too high, theresistances of the resistors 25 and 26 are adjusted relatively toeachother by the magnet 29 so as to increase the current through the fieldwinding I5 and thereby efiect an increase in the voltage of the machineI0. It will be obvious that during the time the battery B is supplyingcurrent to the distribution circuit I, the connections of the resistors23-26 and field winding I5 are such that the magnet 29 may cause thecurrent through the field winding I5 to be reduced to zero and, in fact,to be increased in the opposite direction so as to overcome the residualmagnetism of the field circuit and cause the machine IE to operate as abooster. In this manner, it is possible to supply a much largerproportion of the total charge of the battery B to the distributioncircuit since current may still be supplied to the distribution circuitafter the voltage of the battery has decreased below the voltage whichit is desired to maintain constant across the distribution circuit. I

In the particular arrangement shown in the drawing, the operating magnet29 of the regulator I9 is provided with an anti-hunting winding 33,which is connected in parallel with the field winding I5 through asuitable stabilizing transformer 34 so that any change in the currentthrough the field winding I5 efiects in a manner well known in theregulating art a compensating effect in the magnet 29. Since a currentchange of a predetermined character in the field winding I5 efiects adifferent change in the voltage being maintained constant by theregulator I9 when the battery is being charged than when the battery isbeing dischargechit is necessary in order to obtain the propercompensating effect to reverse the connections between the field winding15 and the antihunting winding 33 whenever the connections of thevoltage winding 23 are changed. For accomplishing this result, I providea reversing relay 35, the energization of which is controlled by theposition of the control relay 6. This reversing relay 35 controls theconnections between the stabilizing transformer 34 and the field windingl so as to reverse these connections whenever the control relay 6changes its position.

The voltage regulator 29 for the dynamoelectrio machine I I is similarto the voltage regulator l9 and comprises two fixed resistors 31 and 38and two adjustable resistors '39 and 49 which are so connected as toform a Wheatstone bridge. The two fixed resistors 37 and 33 and anotherfixed resistor 45 are connected in series between the neutral andnegative conductors of the distribution circuit l, and the adjustableresistors 39 and 49 are connected in a series circuit which is inparallel with the series-connected fixed resistors 31 and 38. Oneterminal of the field winding it is connected to a point between thefixed resistors 5i! and 33, and the other terminal of the field winding[6 is connected to a point between the adjustable resistors 39 and 49.The resistances of the resistors 39 and 49 are arranged to be adjustedby a suitable operating magnet 42 comprising a voltage winding 43, whichis arranged to be connected so as to be energized in response to thevoltage of the battery B when the relay 5 is energized and in responseto the voltage between the neutral and negative terminals of thedistribution circuit i when the relay 1 5 is deenergized. Suitableadjustable resistors 44 and 45 are respectively connected in series withthe voltage winding 43 when it is connected across the battery B andwhen it is connected between the neutral and negative conductors of thedistribution circuit 1 so as to efiect the proper calibration of theregulator when the connections of the voltage winding 43 are changed.The adjustable resistors 39 and 49 are so controlled by the magnet 42that an increase in the energization of the magnet 42 effects anincrease in the resistance of the resistor 39 and a decrease in theresistance of the resistor 49. Therefore, during the normal operation ofthe system when the machine H is operating as a booster to increase thevoltage across the battery B to the desired charging Value, a reversingrelay 46 which is controlled by the relay 9 connects the adjustableresistors 33 and it so that the resistors 31 and 49 are respectively inthe adjacent branches of the Wheatstone bridge which are connected tothe neutral conductor of the distribution circuit I through the resistorand the resistors 38 and 39 are respectively in the adjacent branches ofthe Wheatstone bridge which are connected to the negative conductor ofthe distribution circuit I. When, however, the main supply circuit 2fails so that the battery B supplies current to the distribution circuit1 and the regulator 29 operates to maintain a constant voltage betweenthe neu tral and negative conductors of the distribution circuit i, thereversing relay 49 changes the connections of the resistors 39 and 46 sothat the resistors 91? and 99 are respectively in the adjacent branchesof the Wheatstone bridge which are connected to the neutral conductor ofthe distribution circuit I, and the resistors 98 and 40 are respectivelyin the adjacent branches of the Wheatstone bridge which are connected tothe negative conductor of the distribution circuit l.

V The regulator 29 is also provided with an antihunting winding 41,which is connected in parallel with the field winding it through asuitable stabilizing transformer 48 so that any change in the currentthrough the field winding 16 effects in a manner well known in theregulating art a compensating effect in the magnet 42. A reversing relay49, similar to the reversing relay of the regulator I9, is provided soas to reverse the connections between the field winding !6 and thestabilizing transformer 48 whenever the control relay 6 changes itsposition.

The operation of the arrangement shown in the drawing will be apparentfrom the heretofore description. When the main supply circuit 2 isenergized so that the voltage between the positive and negativeconductors is sufficient to maintain the contact 1 of the relay 5closed, the control relay 6 is energized and its contacts 50 completethe series energizing circuit of the operating windings of thecontactors 3 and 4 to effect the connection of the distribution circuitl to the supply circuit 2. The contacts 5| of the relay 6 completeenergizing circuits for the reversing relays 32, 35, 46, and 49, and thecontacts 52 and 53 of the relay 6 respectively connect the voltagewindings 28 and 43 of the regulators l9 and 20 across the batteries Band B so that the currents through the field windings l5 and [6 areregulated in a well known manner so that predetermined constant chargingvoltages are main tained across the batteries B and B.

In case the main supply circuit 2 fails so that the voltage impressedacross the voltage responsive relay 5 decreases below a predeterminedvalue and effects the opening of the relay contact 1, the control relay6 becomes deenergized, and by opening its contacts 59 effects theopening of the contactors 3 and 4 so as to disconnect the distributioncircuit I from the main supply circuit 2. The opening of the contacts 5|of the control relay 6 effects the deenergization of the reversingrelays 32, 35, 46 and 49 so as to reverse the connections of theadjustable resistors 25, 26, 39 and 49 and the connections of theanti-hunting windings 33 and 4?. By opening its contacts 52 and 53 andclosing its contacts 54 and 55, the control relay 6 effects thedisconnection of the voltage windings 28 and 43 from across thebatteries B and B respectively and effects the connections of thesewindings respectively between the positive and neutral conductors andbetween the neutral and negative conductors of the distribution circuitl. The regulators l9 and 20 then operate in a well known manner toregulate the currents through the field windings l5 and It respectivelyso that predetermined voltages are maintained between the positive andneutral conductors and between the neutral and negative conductors ofthe distribution circuit I.

It will be observed that as the batteries discharge and their terminalvoltages decrease, the bucking voltages of the machines l0 and H aregradually decreased until they become zero, and in some cases, thecurrents through the field windings i5 and I5 may even build up in thereverse direction and cause the machines l9 and H to operate as boostersin order to maintain the desired voltages across the distributioncircuit When the voltage of the supply circuit 2 is again restored toits normal value, the voltage relay 5 picks up and effects theenergization of the control relay 6, which in turn effects thereconnection of the distribution circuit l to the supply circuit 2 andrestores the normal connections of the regulators l9 and so that themachines It! and H operate as boosters to impress the proper chargingvoltages across the batteries B and B.

While I have, in accordance with the patent statutes, shown anddescribed my invention as applied to a particular system and asembodying various devices diagrammatically indicated, changes andmodifications will be obvious to those skilled in the art, and Itherefore aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a system of electric distribution, a source of direct current, adirect current distribution circuit connected to said source, a batteryconnected across said distribution circuit, a variable voltage deviceconnected in series with said battery across said circuit, means fordisconnecting said source from said circuit, and means for regulatingsaid device so as to maintain a predetermined voltage across saidbattery in response to said source being connected to said distributioncircuit and a predetermined voltage across said distribution circuit inresponse to said source being disconnected therefrom.

2. In a system of electric distribution, a source of direct current, adirect current distribution circuit connnected to said source, a batteryconnected across said distribution circuit, a direct currentdynamoelectric machine connected in series with said battery across saidcircuit, means for disconnecting said source from said circuit, andmeans for regulating the voltage of said machine so as to maintain apredetermined voltage across said battery in response to said sourcebeing connected to said circuit and a predetermined voltage across saiddistribution circuit in response to said source being disconnectedtherefrom.

3. In a system of electric distribution, a source or" direct current, adirect current distribution circuit connected to said source, a batteryconnected across said distribution circuit, a direct currentdynamoelectric machine connected in series with said battery across saidcircuit, means .for disconnecting said source from said circuit, vmeansfor regulating the excitation of said machine, and means for controllingsaid regulating means to maintain a predetermined voltage across saidbattery in response to said source being connected to said circuit andto maintain a difierent predetermined voltage across said circuit inresponse to said source being disconnected therefrom.

4. Ina system of electric distribution, a source of direct current, adirect current distribution circuit connected to said source, a batteryconnected across said distribution circuit, a direct currentdynamoelectric machine connected in series with said battery across saidcircuit, means for disconnecting said source from said circuit, meansfor regulating the excitation of said machine to maintain apredetermined voltage across predetermined voltage across said circuitin response to said source being disconnected therefrom, including arelay having a voltage responsive winding, a plurality of resistors,and. means for connecting said voltage responsive winding and one ofsaid resistors across said battery in response to said source beingconnected to said circuit so that said relay responds to a batteryvoltage of a predetermined value and for connecting said voltageresponsive winding and another of said resistors across said circuit inresponse to said source being disconnected therefrom so that said relayresponds to a circuit voltage of a difierent predetermined value.

5. In a system of electric distribution, a threewire source of directcurrent, a three-wire direct current distribution circuit, means forconnecting said circuit to said source, means controlled by the voltageof said source for efiecting the opening of said connecting means inresponse to said voltage decreasing below a predetermined value and forclosing said connecting means in response to said voltage increasingabove a predetermined value, two batteries respectively connectedbetween the positive and neutral conductors and between the neutral andnegative conductors of said circuit, a direct current motor connectedbetween two conductors of said circuit and driving two direct currentdynamoelectric machines the armature windings of which are respectivelyconnected in series with said batteries, and means for respectivelyregulating the voltages of said machines so as to maintain apredetermined voltage across the associated series connected battery inresponse to said connecting means being closed and a predeterminedvoltage between the circuit conductors across which the respectivemachine and series connected battery are connected in response to saidsource being disconnected from said circuit.

6. In a system of electric distribution, a threewire source of directcurrent, a three-wire direct current distribution circuit, means forconnecting said circuit to said source, means controlled by the voltageof said source for effecting the opening of said connecting means inresponse to said voltage decreasing below a predetermined value and forclosing said connecting means in response to said voltage increasingabove a predetermined value, two batteries respectively connectedbetween the positive and neutral conductors and between the neutral andnegative conductors of said circuit, a direct current motor connectedbetween two conductors of said circuit and driving two direct currentdynamoelectric machines the armature windings of which are respectivelyconnected in series with said batteries, a voltage regulator for eachmachine, and means for causing each voltage regulator to control theexcitation of the associated machine so as to maintain a predeterminedvoltage across the associated series connected battery in response tosaid consaid battery in response to said source being connected to saidcircuit and to maintain a difierent necting means being closed and apredetermined voltage between the circuit conductors across which theassociated machine and series connected battery are connected inresponse to said source being disconnected from said circuit.

HAROLD M. MARTIN.

